Reversing and/or preventing obesity during adolescence yields significant cardio-metabolic rewards. Yet, 90% of obese adolescents become obese adults. This highlights the difficulty in reversing obesity once onset occurs. Additionally, progress in preventing childhood obesity has been slow. Despite promising trends, the widening gulf between minorities and lower socio-economic youth and their non-minority, more affluent counterparts threatens our ability to reduce health disparities in the future. Targeting adolescents for obesity prevention holds great promise for stemming high obesity rates. Theoretical, experimental, and epidemiological support for an association between sleep and obesity exists. However, not all short sleepers are overweight/obese and vice versa and extant studies report inconsistent findings. This observational study in a lower socio-economic racially diverse school district in NJ seeks to explore whether chronotype modifies the association between short sleep and obesity in adolescents. This study will be one of the first to explore this association. It will involve collaborative efforts with school nurses, physicians, heath teachers, school district administrators, the parent teacher association, and the community at large, thus exemplifying a strong community partnership. It exemplifies how future nurse scientists may lead the way in providing evidence for bio-behavioral approaches to preventing/reversing obesity in adolescents. This proposal is consistent with the applicant's long-term goal to explore chronobiological factors impacting adolescent obesity and sleep and to establish a program of interdisciplinary research aimed at preventing/reducing childhood obesity and current/future health disparities. Findings from this study will influence policy and clinical practice. Sensitivity of adolescent circadian rhythms to evening light exposure increases the propensity for later chronotypes. Therefore, urban planning and development policies should seek to limit the exposure to light at night by adolescents. Street lighting, field lighting, and community signage should be limited and/or designed to emit lux below a specified threshold in specified areas. School and community athletic policies limiting high school games/practices during late evening hours in lit athletic fields/gymnasiums will also be warranted. Parent/student education coupled with effective strategies for limiting nighttime exposure from light emitting technology will also be important. Screening for late chronotype throughout adolescence will identify those at greatest risk for deleterious metabolic effects. Interventions such as parentally enforced bedtimes, morning light exposure, and support for later high school start times will help maintain circadian alignment limiting deleterious health effects, such as increased BMI, in adolescents with late chronotypes.